Compositions based on hypochlorite bleach are well-known for use in cleaning hard surfaces which are subject to staining and in particular they are known for use as toilet cleaners. The bowls of flushable toilets are subject to deposition of lime scale in hard water areas. This lime scale is predominantly calcium carbonate but may become discoloured by incorporation of coloured metal ions such as ions of Fe, Mn and by bacterial films and human waste deposits on the lime scale or on the surface of the toilet bowl. Aqueous solutions of sodium hypochlorite, usually containing a thickener to increase viscosity, are widely used in treating toilet bowls. The hypochlorite bleaches the lime scale so that it is less noticeable but does not remove it. The hypochlorite also acts as a disinfectant and users often rely on the odour of chlorine released by hypochlorite bleaches as confirmation that disinfection is taking place.
It is possible to remove lime scale by the action of acids but there is a risk of the release of excessive quantities of toxic chlorine gas if such acidic cleaners are inadvertently mixed with sodium hypochiorite bleach. When used alone such acidic cleaners do not produce the slight chlorine odour which reassures users that the toilet bowl is being disinfected. However, there has been no consideration of the possibility of providing some ability to remove lime scale in a hypochlorite bleach.
Sodium salts are generally the cheapest of the alkali and alkali metal salts (with the exception of such insoluble materials as calcium and magnesium carbonates) and in general sodium salts are used whenever a water soluble alkali metal or alkaline earth metal salt is required unless there is some known reason for using another salt. The case of hypochlorite bleaches is no exception and the commercially available toilet cleaners based on hypochlorite bleach use sodium hypochlorite.
Derwent WPI abstract accession number 87-032288/05 of JP-A-61-287995 discloses a two -pack cleaning composition for a flush toilet. One pack comprises bleaching agent and the other pack comprises non-ionic surfactant, water-soluble inorganic salt and water-insoluble inorganic salt. The bleaching agent may be NaClO, KClO, LiClO, Ca hypochlorite, or Na or K dichloroisocyanurate. The use of a two pack composition will be inconvenient. The abstract does not suggest that the use of hypochlorites other than NaOCl has any advantages which would justify the increased cost.
Derwent WPI abstract accession number 87-032283/05 of JP-A-61-287990 discloses a cleaning composition which may be used in flushing toilets, and may be in the form of a liquid, solid, paste, or granules. It comprises a chlorine bleach and and an alkali metal alkyl succinate. The chlorine bleach may be calcium hypochlorite, or sodium or potassium dichloroisocyanurate.
The chlorine bleaches disclosed in this abstract have low solubility in water and are generally supplied commercially as solids. However an important market for chlorine bleaches is as pourable liquids which are poured by the user into the toilet bowl. For this purpose chlorine bleaches having high solubility in water are desirable, namely the water soluble hypochlorite bleaches. The abstract contains nothing which suggests that the use of potassium as opposed to sodium dichloroisocyanurate gives any advantage in lime scale removal. As the first chlorine bleach mentioned is calcium hypochlorite the abstract does not appear to be concerned with the problems caused by the presence of calcium ions.
It is known that various compounds will sequester metal ions, including calcium ions. However, sequestering agents are usually employed to prevent metal ions, such as calcium, precipitating from aqueous solution. In a conventional liquid toilet cleaner poured by the user from a container into the bowl of a flushing toilet the only water affected by the contents of the liquid cleaner is the water initially held in the toilet bowl and the first flush of water used to remove the toilet cleaner. Most of the water passing through the toilet bowl will be unaffected by the contents of the liquid cleaner. There would thus appear to be no advantage in introducing sequestering agents into conventional liquid hypochlorite bleach.
We have now found that the bowls of flushing toilets can be more effectively cleaned by treating them with a liquid hypochlorite bleach with a defined additive.